Liquid petroleum gas vaporizer system



Jan. 26, 1960 w. P. FREEMAN, JR

LIQUID PETROLEUM GAS VAPORIZER SYSTEM Filed Aug. 27, 1956 United States 'Patent LIQUID PETROLEUM GAS vAPoRIzER SYSTEM William P. Freeman, Jr., Dallas, Tex., assignor to John E. Mitchell Company, Dallas, Tex., a corporation of Missouri Application August 27, 19s6,seria1 No. 606,262

13 claims. (ci. s2-ss) The present invention relates to a vaporizer system for liquid petroleum gas and the like.

' Such systems have heretofore been made, but they have presented ditliculties of operation when used in cold climates because of reduction of vapor pressure and the condensing of the vaporized gas. At times it is diticult, if not impossible, to get a flow of the liquid petroleum gas to the vaporizer and of vaporized gas from the vaporizer to the point of use.

The 4present invention is designed to overcome these difliculties. Conventionally, the storage tank for the liquid petroleum gas is connected by a gravity-How pipe into a vaporizer. The vaporizer maintains a liquid level in-its area subjected to heat, that is automatically vadjusted by the generated vapor pressure so that the :amount of vaporization will balance the load requirements. The vaporizer is subjected to heat at the bottom.

The vapor outlet line has pressure regulators in it. Usually there is a rst stage regulator that partially reduces the pressure, and a second stage regulator that further reduces the pressure to some value such as 11 inches of water, which is a conventional usable pressure for gas.

It has heretofore been a problem to keep the liquid owing into the vaporizer when the air temperatures are very cold. For example, when normal butane is the LP. gas being used, if the air temperature should get down to 32 F., there would be such a low pressure in the tank itself that the 'liquid is not permitted to flow to the vaporizer at all. To overcome this, the applicant has. provided a pressure pump that is automatically put in operation when the pressure within the tank getsbelow a certain value. This has required a controlled bypass line that permits the liquid to be driven back vfrom the vaporizer into the storage tank despite the pump.

Additionally, the cold weather causes the vapor from the vaporizer to condense. Inevitably the piping from the vaporizer to the point of use has low spots in it. Frequently where the vaporizer is mounted outside of a house, the pipe is carried from the vaporizer down into the ground, thence along underground and nally up into the house. When the temperature is low, the vapor tends to condense in this cold, low, area of the piping. When such condensing takes place, there is the possibility of driving liquid into the household appliances designed to operate on vapor. Y

The applicant has overcome the second diliic'ulty by a by-pass line that, in the preferred arrangement,eextends back to the storage tank from` a point adjacent but subsequent to a low` area in the piping, between the two regulators, with an automatic thermostatic control that shunts the vapor flow back to the tank whenever the temperature within'this by-pass or shunt line gets below a certain value.

The foregoing arrangementprovides a system that will work, despite extremely cold weather and which automatically takes care of the condensing problem.

@falce Jones-Patent 2,526,363, the vaporizer being connected to,

the tank by pipe 12.

A ny suitable heating means is used adjacent the bot- V` tom of the vaporizer 11 causing the liquid to vaporize and build up vapor'pressure. Here an electric heating element H has been illustrated solely to typify heating means. The pressure in the top of-the vaporizer causes the vapor to attempt to` flow out an `outlet pipe 13 in which is located a first stage regulator 14, that may be set to maintain some downstream pressure such as 30 p.s.i. If the consumption of gas is less than that generated by heating the liquid, the regulator 14 will throttle down and the pressure back of it will build up. The pressure will drive the liquid from the vaporizer 11 backwards throuph pipe 12 (and as will appear, through the -by-pass pipe) to the storage tank, thereby reducing the amount of liquid in contact with the heated part of the vaporizer 11. Reduction of amount of liquid in contact with the heating surface of the vaporizer 11, causes reduction in the amount of liquid being vaporized, until the amount is equalized with the load requirements.

The Vforegoing has not been shown in detail here because it is well known to the art, including the patent referred to. The parts have not been shown in their specific relative sizes or positions, for the same reason. l

Oonventionally, there is a vapor line 16 that extends from the top of the storage tank 10 to the top of theV vaporizer 11 so that any vapor in the storage tank may be used as needed, and as it is available, thereby saving the requirement of generating that amount. The line 16 contains some form of check-valve 17 that permitsy `In the foregoing system, there is an electric (or other) i pump 25 in theliquid supply line 12 between the storage tank and the vaporizer. This pump 25 is designed to force the liquid to the vaporizer because, under cer-v tain conditions where it is very cold, the liquid may not flow at all. There is a pressure-responsive switch 26 that controls the pump, as will appear.

A back ow pipe 27, is connected into the pipe 12,

downstream from the pump 25. It is also connected.

through a pressure relief-valve 28 and a check-valve 29 into the top of the storage tank. The check-valve .permits ow back Vto the tank 10 but not from the tank.

' There is a by-pass pipe 30 connected into the pipe 22 downstream from the condensing section 21,but ahead of the second stage regulator 23. The pipe 30 is brought down and underground atj31, and finally rises again atv 32, thence through a thermostatic controlvalve 34, a

check-valve 36j and into the top -of the storage tank 10.I Thev thermostatic control valve 34 has a control sensing,

bulb 35 that causes this valve 34 to be closed except when temperature of the sensing bulb 35 is below the predetermined value. While it is ordinarily preferable to use a thermostatic control 34 with the bulb 35, it should be recognized that pressure and temperature are, interrelated functions, so that a pressure`controlled`valve 34 couldj be used, responsive, to the pressure changes that correspond to the temperature changesv here set forth.

Operation In-normal operation, where the surrounding temperatures aremoderate, the vaporizer 1-1= will operate in the usual manner, without the assistance ofthe pump, the

liquidl fuelY beingforced` fromthe.. tank 1Y0 through they pipe 12` into thevaporizer 111i, by-reason of the pressure differential. 'lheheater H, or-whatever-'suitableA heating means is provided, will tend to produce vaporization ofV whatever liquid. is)V within the-vaporizer 11. Butsince the fir-st stage regulator- 1=4 restricts the out-how of liquid,

there may be more-vapor generated-thanis required. AsV

a. result, the pressure in theline 13 inthe top of the vaporizerwill. build` up, and will drive the liquid backwardly into the tank 1-0; therebyreducing the amount of liquid exposed to-theheated area of the vaporizer and reducing the amount ofi vapor generated, until itequals the amount to be consumed'.

The vapor is drivenfrom the first stage regulator through the pipe 24)! tothe second stage regulator andthere reduced in pressure, v

Invery cold weather, the pressure within-thetank may go down to such al deg-reethat it is below atmospheric pressure, and then therewill be a tendency to drive 12 and into the pipe 27. When the pressure in the pipe4 27 rises to a certain-value, the pump will be stopped. No more liquid will be driven into the vaporizer until the excessive pressure in the vaporizer is reduced. Thereafter the pump will be automatically turnedV on or. ofr, depending upon the` condition at the pressure switch which, in turn, is the'function of the pressure in the topof the vaporizer.

In the event that, for some reason, there remains an excessive pressure in the top of the vaporizer, even after the pump is turned off, thiscondition canV be relieved through the relief-valve 28. If the pressure at the reliefvalve rises to a point (such as 30 p.s.i.), this valve 28 will open and the liquid may bedriven past the check-valve 29-and back into the storageV tank.

This relief can take place, as a matter of fact, even if the pump continues to run inadvertently. Hence it not only provides the back-flow. function, but also adds a safety. feature to prevent excessive pressure in the vaporizer if the pump fails to shut olf.

When the vapor leaves the first stage regulator and passes` through the pipe into. the underground portion 21 it may condense invcold weather. Indeed, it may condense at any point up to the secondi stage regulator and drop back into then portion 21 as a liquid. This condensation may accumulate even when there is no demand for gas because the vaporizer is designed to maintain the pressure in the piping 20 corresponding to the setting of' the regulator. As the gas condenses, it lowers pressure in the piping 20, which acts as an accumulator for the liquid. With such pressure reduction, more vapor is delivered to the piping to restore the pressure, and further condensation can occur. Liquid collected there might be forced into the house pipe 24 and' into the gas-consuming appliances, which is danger- 4 ous, and it can create a false pressure in the regulator 14 and drive the liquid all out of vaporizer 11, stopping the system, even though there may be a demand for gas from the pipe 24.

To eliminate this situation, the by-pass pipe 30-31- 32 is provided, this being connected into the pipe 22 ahead of the second stage regulator 23. When the ground temperature at bulb 35 goes below a predetermined value, at which condensing can take place, the valve 34 opens; This. opens the whole return by-passline. Thereupon the pressure back of the second stage regulator 23 will drive hot vapor through the pipes 20, 21, 22, 30, 3.1 and 32v therebyT heating this piping sutiiciently to avoid condensing of the vapor therein. The vaporizer is automatically operated. to. supply such vapor, as will be understood. Should there be any condensate in the pipe 21, the vapor pressure will force it back through the by-pass, into the storage tank, although usually` it will revaporize in the. by-pass. y

Of course, the foregoing action cannot occur if the storage tank pressure is greater than that at the downstream side of the first stage regulator 14'. If it be assumed that the regulator14 provides a pressure of 30 or vso,p.s.i., in cold weather the vapor pressure of thel L.P.G. will be considerably lower than that. In warm weather, the vapor pressure in the tank can exceed 30- p.s.i., so that the b'y-(pass is ineffective. This is an advantage as it provides an automatic summer cut-out of the cold-weatherY by-pass.

In short, this feature is that condensation outside the building will beanticipated and automatically prevented, or if it occurs, the liquid'l will bev driven back into'the tank, when (a) the temperature at sensing bulb 35 indicates a conditionI cold enough for condensation to occur, and consequently opens valve 34 and (b) when the pressure on the downstream side of the irst stage reguiator is higher than the vapor pressure in the tank 10.

The foregoing demonstrates that the present system makes L.P.G. vaporization usable in cold climates.

What is claimed is: l

1. A vaporizing system of the kind described, comprising a storage tank for vaporizable liquid, a vaporizer connected to the tank by a supply pipe that conducts vaporizable liquid to the vaporizer, an outlet pipe from the upper part of the vaporizer iadapted to be connected to a vapor consuming apparatus, the outlet pipe having a condensate-entrapping portion downstream. ofl the pressure regulator hereafter recited, a pressure regulator in the outlet pipe, to limit the vapor pressure on` its downstream side to a predetermined maximum; a

return by-pass pipe connected into the outlet pipe at aV point spaced downstream from the regulator to receive and carry o the condensate in thel outlet pipe, and leading back to the storage tank, a thermostatically controlled valve in thel by-pass pipe, normally closed but thermostatically opened when the temperature adjacent the system becomes low enough toA condense the vapor; whereby the vapor pressure downstream of the regulator may drive condensed vapor through the by-pass pipe back to the tank.A

2. A system as in claimA 1, wherein there is a second stage pressure regulator in the outlet pipe down-stream of the by-pass connection, and the outlet, between the rst regulator and the by-pass, has a low part constituting the entrapping portion wherein condensate may collect.

3. A system `as in claim l, wherein the vaporizer and tank are outdoors, and the outlet pipe leads from the regulator and goes underground, then up, and the bypassV isconnected into the outlet pipe subsequent to the underground part.

4. A vaporizing system including a storage tank for v vaporizable liquid, a supply pipe therefrom, a vaporizer let from the vaporizer, a pressure regulator in the outlet adapted to limit the outlet pressure on its downstream side, a low area in the outlet upstream from the regulator whereat condensed Vapor may collect, a by-pass pipe connected with the outlet downstream of the low area and upstream of the regulator, the by-pass pipe leading back into the tank; and a thermostatically regulated valve in the by-pass, normally closed, but opened when the temperature adjacent the `system descends below a condensing value.

5. The system of claim 4, wherein the low area in the outlet is underground, and the by-pass pipe extends underground, with the thermostatic valve sensitive to ground temperatures adjacent the by-pass pipe.

6. The system of claim 4, wherein there is a first stage pressure regulator in the outlet upstream of the low area, set to maintain a pressure on its downstream side higher than the vapor pressure of the liquid at the temperature of condensing.

7. A vaporizing system for vaporizable liquid, comprising a storage tank; a vaporizer wherein the liquid may be vaporized to produce vapor under pressure, a liquid supply pipe from the tank to the vaporizer, a vapor discharge pipe from the vaporizer, means to restrict flow of vapor through the discharge pipe., the vapor discharge pipe having a condensed liquid-catching trap-like part upstream from the restricting means and below the vaporizer a by-pass return line from that part back to the tank to conduct condensed vapor therefrom land a valve in the bypass line.

8. A vaporizing system for vaporizable liquid, comprising a storage tank; a vaporizer wherein the liquid may be vaporized to produce vapor under pressure, a liquid supply pipe from the tank to the vaporizer, a vapor discharge pipe from the vaporizer, the vapor discharge pipe having a condensed liquid-catching low-level, traplike part, and a by-pass return line from that part back to the tank to conduct condensed vapor therefrom, pump means to force liquid from the tank to the vaporizer through the supply line, and a back ow line downstream from the pump and connecting the vaporizer with the tank.

9. The system of claim 7, plus a control automatically responsive to predetermined physical conditions of the environment of thevbypass line, and a valve operated thereby, the valve being in the by-pass line to close the same when condensing conditions do not exist.

10. The system of claim 9, wherein the control is a thermostatic device responsive to temperatures adjacent parts of the system subject to condensing of the vaporized gas.

11. The system of claim 9, wherein there is a pressure-reducing device in the vapor discharge pipe downstream from the by-pass.

l2. A vaporizing system for volatile liquids: including `a storage tank, a vaporizer, a liquid-pipe from the tank to ythe vaporizer, a heating means to supply heat to a part of the vaporizer, a vapor outlet from the vaporizer, a restricting means in the outlet, the outlet leading to a point of vapor consumption, the increase of pressure in the vaporizer driving the liquid back therefrom to reduce generation of vapor; a pump in the liquid pipe to drive liquid into the vaporizer, a back ilo-w pipe from the high pressure side of the pump yand the lower part of the vaporizer back to the tank, and a relief valve in the back ow pipe, the relief valve opening when vaporizer pressure exceeds a predetermined value, to enable such pressure to drive liquid from the vaporizer to reduce the rate of vaporization despite the action of the pump.

13. The combination `of claim 12, together with a pressure-responsive device to stop the pump when the vaporizer pressure requires exclusion o-f liquid from the vaporizer.

References Cited in the le of this patent UNITED STATES PATENTS 2,348,546 Kereher May 9, 1944 2,402,355; Whaley June 18, 1946 2,443,724 Cibulka June 22, 1948 2,463,477 Buttner Mar. 1, 1949 2,499,355 Buttner Mar. 7, 1950 2,576,984 Wildhack Dec. 4, 1951 2,618,935 Malir Nov. 25, 1952 2,747,374 Thompson May 29, 1956 

